How does the urethral sphincter work?

The urethral sphincter works by contracting and relaxing muscles.

The urethral sphincter is located at the end of the urethra and consists mainly of annular muscle fibers. These muscle fibers surround the urethra to form a ring structure that tightly closes the urethra and prevents involuntary urine from escaping. The urethral sphincter works mainly by contracting and relaxing muscles. When the bladder is full of urine, the brain sends signals to the nerves of the urethral sphincter to relax, thereby opening the urethra and allowing urine to escape. When the bladder is not full of urine or when urination needs to be stopped temporarily, the urethral sphincter will remain contracted to close the urethra tightly and prevent urine leakage.